Process for producing mixture of dihydroxydiphenylsulfone isomers

ABSTRACT

The present invention provides a process for producing a mixture of dihydroxydiphenylsulfone isomers containing 2,4′-dihydroxydiphenylsulfone, the process comprising heating 4,4′-dihydroxydiphenylsulfone or a mixture of dihydroxydiphenylsulfone isomers containing at least 85 wt. % of 4,4′-dihydroxydiphenylsulfone in the presence of phenol and sulfuric or sulfonic acid.

TECHNICAL FIELD

[0001] The present invention relates to a process for producing amixture of dihydroxydiphenylsulfone isomers containing2,4′-dihydroxydiphenylsulfone.

BACKGROUND ART

[0002] Among various phenolic compounds, 2,4′-dihydroxydiphenylsulfone(hereinafter occasionally referred to as 2,4′-DDS) has recentlyattracted attention because of its great utility as a color developerfor heat-sensitive paper.

[0003] Known methods for producing 2,4′-DDS include the separation andpurification of 2,4′-DDS from mixtures containing 2,4′-DDS and4,4′-dihydroxydiphenylsulfone (hereinafter occasionally referred to as4,4′-DDS).

[0004] Moreover, it is known that when 4,4′-DDS is heated in a phenolsolvent in the presence of an acid catalyst, isomerization occurs,thereby producing a mixture of dihydroxydiphenylsulfone isomerscontaining 4,4′-DDS and 2,4′-DDS in a weight ratio of about 75 to about25 (isomerization equilibrium) (Journal of the Chemical Society ofJapan, 1985 (1), 70-74). However, since this isomerization reactionrequires 20 hours or longer to reach isomerization equilibrium evenunder heating conditions of 190° C. or higher, it is difficult to employthis isomerization reaction industrially.

DISCLOSURE OF THE INVENTION

[0005] An object of the invention is to provide a process for producinga mixture of dihydroxydiphenylsulfone isomers containing an enhancedamount of 2,4′-DDS, the process being able to induce isomerizationequilibrium in a short period of time when 4,4′-DDS is isomerized.

[0006] Other objects and characteristics of the present invention willbecome evident by the disclosure provided hereinbelow.

[0007] The inventors conducted extensive research and found that heating4,4′-DDS in the presence of specific amounts of phenol and sulfuric acidcan induce isomerization equilibrium in a short period of time. Thepresent invention has been accomplished based on this finding.

[0008] Furthermore, the inventors found that heating 4,4′-DDS in thepresence of phenol and sulfonic acid can induce isomerizationequilibrium in a short period of time. The present invention has beenaccomplished based also on this finding.

[0009] In other words, the present invention provides processes forproducing a mixture of dihydroxydiphenylsulfone isomers as describedbelow:

[0010] 1. A process for producing a mixture of dihydroxydiphenylsulfoneisomers containing 2,4′-dihydroxydiphenylsulfone, the process comprisingheating 4,4′-dihydroxydiphenylsulfone to a temperature of 160° C. orhigher in the presence of an equal weight or less of phenol and 20 mol %or less of sulfuric acid relative to the 4,4′-dihydroxydiphenylsulfone.

[0011] 2. A process for producing a mixture of dihydroxydiphenylsulfoneisomers containing 2,4′-dihydroxydiphenylsulfone, the process comprisingheating a mixture of dihydroxydiphenylsulfone isomers containing4,4′-dihydroxydiphenylsulfone in a proportion of at least 85 wt. % to atemperature of 160° C. or higher in the presence of an equal weight orless of phenol and 20 mol % or less of sulfuric acid relative to themixture.

[0012] 3. A process for producing a mixture of dihydroxydiphenylsulfoneisomers containing 2,4′-dihydroxydiphenylsulfone, the process comprisingheating 4,4′-dihydroxydiphenylsulfone in the presence of phenol andsulfonic acid.

[0013] 4. A process for producing a mixture of dihydroxydiphenylsulfoneisomers containing 2,4′-dihydroxydiphenylsulfone, the process comprisingheating a mixture of dihydroxydiphenylsulfone isomers containing4,4′-dihydroxydiphenylsulfone in a proportion of at least 85 wt. % inthe presence of phenol and sulfonic acid.

[0014] Hereinbelow, the process for producing a mixture ofdihydroxydiphenylsulfone isomers of the present invention is describedin more detail:

[0015] [Process Employing Sulfuric Acid]

[0016] As a single starting material of the present invention, 4,4′-DDSmay have a purity of 99% or higher.

[0017] A mixture of dihydroxydiphenylsulfone isomers containing 4,4′-DDSin a proportion of at least 85 wt. % can also be used as a startingmaterial. It is preferable that this isomeric mixture contains 2,4′-DDSas another isomer.

[0018] The starting material, i.e., 4,4′-DDS or a mixture ofdihydroxydiphenylsulfone isomers containing 4,4′-DDS in a proportion ofat least 85 wt. %, is isomerized by heating in the presence of phenoland sulfuric acid.

[0019] Phenol is used in a weight equal to or less than, and preferablyin a weight of 0.1 to 0.8 times as much as, the starting material, i.e.,4,4′-DDS or a mixture of dihydroxydiphenylsulfone isomers containing4,4′-DDS.

[0020] Sulfuric acid is used in a proportion of 20 mol % or less, andpreferably in a proportion of 1 to 10 mol %, based on the startingmaterial, i.e., 4,4′-DDS or a mixture of dihydroxydiphenylsulfoneisomers containing 4,4′-DDS.

[0021] Solvents may or may not be used. When solvents are used, heat-and acid-resistant solvents such as sulfolane and the like arepreferable.

[0022] The reaction temperature for conducting isomerization is 160° C.or higher, and preferably 170 to 210° C. Isomerization can be conductedunder pressure as necessary.

[0023] The reaction time is not limited. The reaction may be continueduntil isomerization equilibrium. The preferable reaction time is 0.1 to15 hours, and more preferable is 0.5 to 10 hours.

[0024] The desired product of the present invention, i.e., a mixture ofdihydroxydiphenylsulfone isomers containing 2,4′-DDS, is primarilycomposed of 4,4′-DDS and 2,4′-DDS. Preferable is a mixture containing2,4′-DDS in a proportion of 15 to 30 wt. %, more preferable is a mixturecontaining 2,4′-DDS in a proportion of 20 to 30 wt. %, and especiallypreferable is a mixture containing 2,4′-DDS in a proportion of 22 to 30wt. %.

[0025] 2,4′-DDS can be separated from a mixture ofdihydroxydiphenylsulfone isomers containing 2,4′-DDS produced accordingto the invention using known separation and purification methods.

[0026] According to the process of the present invention, when 4,4′-DDSis isomerized, isomerization equilibrium is achieved in a short periodof time, and a mixture of dihydroxydiphenylsulfone isomers containing anenhanced amount of 2,4′-DDS can be obtained.

[0027] [Process Employing Sulfonic Acid]

[0028] As a single starting material of the present invention, 4,4′-DDSmay have a purity of 99% or higher.

[0029] A mixture of dihydroxydiphenylsulfone isomers containing 4,4′-DDSin a proportion of at least 85 wt. % can also be used as a startingmaterial. It is preferable that this isomeric mixture contains 2,4′-DDSas another isomer.

[0030] The starting material, i.e., 4,4′-DDS or a mixture ofdihydroxydiphenylsulfone isomers containing 4,4′-DDS in a proportion ofat least 85 wt. %, is isomerized by heating in the presence of phenoland sulfonic acid.

[0031] Phenol is used preferably in a weight twice as much as or lessthan, and more preferably in a weight 0.1 to 1 times as much as, thestarting material, i.e., 4,4′-DDS or a mixture ofdihydroxydiphenylsulfone isomers containing 4,4′-DDS.

[0032] Examples of sulfonic acids usable in the invention includebenzenetrisulfonic acid, benzenedisulfonic acid, chlorobenzenedisulfonicacid, toluenesulfonic acid, phenolsulfonic acid, and like aromaticmono-, di-, or trisulfonic acids; methanesulfonic acid, ethanesulfonicacid, trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, andlike optionally-fluorinated aliphatic sulfonic acids; Nafion® and likepolymeric sulfonic acids; etc. Among these sulfonic acids, aromaticmono-, di-, or trisulfonic acids are preferable; and benzenedisulfonicacid, toluenesulfonic acid, and the like are more preferable.

[0033] Sulfonic acid is used preferably in a proportion of 20 mol % orlower, and more preferably in a proportion of 1 to 10 mol %, based onthe starting material, i.e., 4,4′-DDS or a mixture ofdihydroxydiphenylsulfone isomers containing 4,4′-DDS.

[0034] Solvents may or may not be used. When solvents are used, heat-and acid-resistant solvents such as sulfolane and the like arepreferable.

[0035] The reaction temperature for conducting isomerization ispreferably 160° C. or higher, and more preferably 170 to 210° C.Isomerization can be conducted under pressure as necessary.

[0036] The reaction time is not limited. The reaction may be continueduntil isomerization equilibrium. The preferable reaction time is 0.1 to15 hours, and more preferable is 0.5 to 10 hours.

[0037] The desired product of the present invention, i.e., a mixture ofdihydroxydiphenylsulfone isomers containing 2,4′-DDS, is primarilycomposed of 4,4′-DDS and 2,4′-DDS. Preferable is a mixture containing2,4′-DDS in a proportion of 15 to 30 wt. %, more preferable is a mixturecontaining 2,4′-DDS in a proportion of 20 to 30 wt. %, and especiallypreferable is a mixture containing 2,4′-DDS in a proportion of 22 to 30wt. %. 2,4′-DDS can be separated from a mixture ofdihydroxydiphenylsulfone isomers containing 2,4′-DDS produced accordingto the invention using known separation and purification methods.

[0038] According to the process of the present invention, when 4,4′-DDSis isomerized, isomerization equilibrium is achieved in a short periodof time, and a mixture of dihydroxydiphenylsulfone isomers containing anenhanced amount of 2,4′-DDS can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

[0039] Examples are given below to illustrate the invention in moredetail.

EXAMPLE I-1

[0040] To 100 g (0.4 mol) of dihydroxydiphenylsulfone (containing4,4′-DDS in a proportion of 99.8 wt. % and 2,4′-DDS in a proportion of0.1 wt. %; hereinafter referred to as bisphenol S (1)) were added 50 gof phenol and 1.6 g (0.016 mol, 4 mol % relative to bisphenol S (1)) of98% sulfuric acid. The mixture was heated to 195° C. and stirred at thistemperature. The results of HPLC (high performance liquidchromatography) analysis conducted after 2 hours of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of85:15, and the mixture after 6 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio of 76:24.

EXAMPLE I-2

[0041] To 100 g of bisphenol S (1) were added 50 g of phenol and 4 g(0.04 mol, 10 mol % relative to bisphenol S (1)) of 98% sulfuric acid.The mixture was heated to 180° C. and stirred at this temperature. Theresults of HPLC analysis conducted after 2 hours of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of86:14, and the mixture after 6 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio of 76:24.

EXAMPLE I-3

[0042] To 100 g of bisphenol S (1) were added 50 g of phenol and 4 g(0.04 mol, 10 mol % relative to bisphenol S (1)) of 98% sulfuric acid.The mixture was heated to 210° C. and stirred at this temperature. Theresults of HPLC analysis conducted after 1 hour of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of75:25, and the mixture after 2 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio of 73:27.

EXAMPLE I-4

[0043] To 100 g (0.4 mol) of dihydroxydiphenylsulfone (containing4,4′-DDS in a proportion of 86 wt. % and 2,4′-DDS in a proportion of 14wt. %; hereinafter referred to as bisphenol S (2)) were added 50 g ofphenol and 1.6 g (0.016 mol, 4 mol % relative to bisphenol S (2)) of 98%sulfuric acid. The mixture was heated to 195° C. and stirred at thistemperature. The results of HPLC analysis conducted after 2 hours ofstirring revealed that the mixture contained 4,4′-DDS and 2,4′-DDS in aweight ratio of 79:21, and the mixture after 6 hours of stirringcontained 4,4′-DDS and 2,4′-DDS in a weight ratio of 75:25.

COMPARATIVE EXAMPLE I-1

[0044] To 15 g (0.06 mol) of bisphenol S (1) were added 36 g of phenoland 3 g (0.03 mol, 50 mol % relative to bisphenol S (1)) of 98% sulfuricacid. The mixture was heated to 195° C. and stirred at this temperature.The results of HPLC analysis conducted after 2 hours of stirringrevealed that the mixture contained 4,4′-DDS and 2,4′-DDS in a weightratio of 88:12, the mixture after 6 hours of stirring contained 4,4′-DDSand 2,4′-DDS in a weight ratio of 82:18, and the mixture after 20 hoursof stirring contained 4,4′-DDS and 2,4′-DDS in a weight ratio of 78:22.

EXAMPLE II-1

[0045] To 100 g (0.4 mol) of bisphenol S (1) were added 100 g of phenoland 5 g (0.02 mol, 5 mol % relative to bisphenol S (1)) ofbenzenedisulfonic acid. The mixture was heated to 180° C. and stirred atthis temperature. The results of HPLC analysis conducted after 2 hoursof stirring revealed that the mixture contained 4,4′-DDS and 2,4′-DDS ina weight ratio of 81:19, and the mixture after 6 hours of stirringcontained 4,4′-DDS and 2,4′-DDS in a weight ratio of 77:23.

EXAMPLE II-2

[0046] To 100 g of bisphenol S (1) were added 50 g of phenol and 3 g(0.017 mol, 4 mol % relative to bisphenol S (1)) of toluenesulfonicacid. The mixture was heated to 195° C. and stirred at this temperature.The results of HPLC analysis conducted after 2 hours of stirringrevealed that the mixture contained 4,4′-DDS and 2,4′-DDS in a weightratio of 79:21, and the mixture after 6 hours of stirring contained4,4′-DDS and 2,4′-DDS in a weight ratio of 75:25.

EXAMPLE II-3

[0047] To 100 g of bisphenol S (1) were added 50 g of phenol and 6.9 g(0.04 mol, 10 mol % relative to bisphenol S (1)) of toluenesulfonicacid. The mixture was heated to 180° C. and stirred at this temperature.The results of HPLC analysis conducted after 2 hours of stirringrevealed that the mixture contained 4,4′-DDS and 2,4′-DDS in a weightratio of 86:14, and the mixture after 6 hours of stirring contained4;4′-DDS and 2,4′-DDS in a weight ratio of 76:24.

EXAMPLE II-4

[0048] To 100 g of bisphenol S (1) were added 50 g of phenol and 6.9 g(0.04 mol, 10 mol % relative to bisphenol S (1)) of toluenesulfonicacid. The mixture was heated to 210° C. and stirred at this temperature.The results of HPLC analysis conducted after 1 hour of stirring revealedthat the mixture contained 4,4′-DDS and 2,4′-DDS in a weight ratio of75:25, and the mixture after 2 hours of stirring contained 4,4′-DDS and2,4′-DDS in a weight ratio Of 73:27.

EXAMPLE II-5

[0049] To 100 g (0.4 mol) of bisphenol S (2) were added 50 g of phenoland 3 g (0.017 mol, 4 mol % relative to bisphenol S (2)) oftoluenesulfonic acid. The mixture was heated to 195° C. and stirred atthis temperature. The results of HPLC analysis conducted after 2 hoursof stirring revealed that the mixture contained 4,4′-DDS and 2,4′-DDS ina weight ratio of 77:23, and the mixture after 6 hours of stirringcontained 4,4′-DDS and 2,4′-DDS in a weight ratio of 75:25.

COMPARATIVE EXAMPLE II-1

[0050] To 15 g (0.06 mol) of bisphenol S (1) were added 36 g of phenoland 3 g (0.03 mol, 50 mol % relative to bisphenol S (1)) of 98% sulfuricacid. The mixture was heated to 195° C. and stirred at this temperature.The results of HPLC analysis conducted after 2 hours of stirringrevealed that the mixture contained 4,4′-DDS and 2,4′-DDS in a weightratio of 88:12, the mixture after 6 hours of stirring contained 4,4′-DDSand 2,4′-DDS in a weight ratio of 82:18, and the mixture after 20 hoursof stirring contained 4,4′-DDS and 2,4′-DDS in a weight ratio of 78:22.

1. A process for producing a mixture of dihydroxydiphenylsulfone isomerscontaining 2,4′-dihydroxydiphenylsulfone, the process comprising heating4,4′-dihydroxydiphenylsulfone to a temperature of 160° C. or higher inthe presence of an equal weight or less of phenol and 20 mol % or lessof sulfuric acid relative to the 4,4′-dihydroxydiphenylsulfone.
 2. Aprocess for producing a mixture of dihydroxydiphenylsulfone isomerscontaining 2,4′-dihydroxydiphenylsulfone, the process comprising heatinga mixture of dihydroxydiphenylsulfone isomers containing4,4′-dihydroxydiphenylsulfone in a proportion of at least 85 wt. % to atemperature of 160° C. or higher in the presence of an equal weight orless of phenol and 20 mol % or less of sulfuric acid relative to themixture.
 3. A process for producing a mixture ofdihydroxydiphenylsulfone isomers containing2,4′-dihydroxydiphenylsulfone, the process comprising heating4,4′-dihydroxydiphenylsulfone in the presence of phenol and sulfonicacid.
 4. A process for producing a mixture of dihydroxydiphenylsulfoneisomers containing 2,4′-dihydroxydiphenylsulfone, the process comprisingheating a mixture of dihydroxydiphenylsulfone isomers containing4,4′-dihydroxydiphenylsulfone in a proportion of at least 85 wt. % inthe presence of phenol and sulfonic acid.
 5. A process for producing amixture of dihydroxydiphenylsulfone isomers containing2,4′-dihydroxydiphenylsulfone, comprising: providing, as a singlestarting material, 4,4′-dihydroxydiphenylsulfone or a mixture ofdihydroxydiphenylsulfone isomers containing4,4′-dihydroxydiphenylsulfone in a proportion of at least 85 wt. %; andheating the starting material to a temperature of 160° C. or higher inthe presence of phenol in an amount equal to or less than the startingmaterial by weight and sulfuric acid in an amount of 20 mol % or lessrelative to the starting material to isomerize the starting material,thereby obtaining a mixture of dihydroxydiphenylsulfone isomerscontaining 2,4′-dihydroxydiphenylsulfone.
 6. The process according toclaim 5, wherein the mixture of dihydroxydiphenylsulfone isomerscontains 2,4′-dihydroxydiphenylsulfone in an amount 15-30 wt. %.
 7. Theprocess according to claim 5, wherein the starting material is heated to170-210° C.